This application pertains to radio frequency transmitters and more particularly to a trainable radio frequency transceiver for remotely controlling one or more devices.
A trainable transmitter for remotely actuating a garage door opening mechanism is disclosed in U.S. patent application No. 07/567,390, filed Aug. 14, 1990, and entitled ELECTRICAL CONTROL SYSTEM FOR VEHICLE OPTIONS. This trainable transmitter learns radio frequency control signals of the type used to remotely actuate devices, such as garage door opening mechanisms used in the United States. In a learning mode, the transceiver identifies the carrier frequency and code of a control signal transmitted by a radio frequency remote control. In a transmitting mode, the transmitter emits a control signal having the carrier frequency and the code of the learned signal.
An improved trainable transmitter having additional advantages and characteristics was developed from the transmitter disclosed in application 07/567,390, and is the subject matter of United States patent application 07/874,361, entitled VEHICLE ACCESSORY TRAINABLE TRANSMITTER filed on Apr. 24, 1992. The improved transmitter includes novel amplitude control, signal identification techniques, and signal storage techniques.
Although these transmitters provide novel, versatile trainable transmitters, it remains desirable to provide additional improvements in the operating characteristics of the transmitter. One difficulty is the trainable transmitter includes receiver components for inputing the control signals in the training mode which introduce noise into the output signal in the transmission mode. An additional difficulty is providing a gain control for adjusting the output level of the transmitter such that it complies with the FCC requirements over the entire frequency range of the transmitter and effectively compensates for inherent variations in the signal strength of the transmitter at different frequencies.